xcenter=`convert <image> -format "%[fx:(w-1)/2]" info:` ycenter=`convert <image> -format "%[fx:(h-1)/2]" info:` see http://www.imagemagick.org/script/fx.php http://www.imagemagick.org/Usage/transform/#fx_escapes >How do you calculate this? I'd like to do something like that in one of >my PHP scripts so folks could input some values and it is autocalculated.